[RocksJava] Fix NativeLibraryLoader

- Resolve problem while using a temporary data folder
- Fix test

java/Makefile

@@ -172,7 +172,7 @@ java_test: resolve_test_deps
 	javah -cp $(MAIN_CLASSES):$(TEST_CLASSES) -d $(NATIVE_INCLUDE) -jni $(NATIVE_JAVA_TEST_CLASSES)
 
 test: java resolve_test_deps java_test
-	java -ea -Xcheck:jni -Djava.library.path=target -cp "$(MAIN_CLASSES):$(TEST_CLASSES):$(JAVA_TESTCLASSPATH)" org.rocksdb.test.RocksJunitRunner $(JAVA_TESTS)
+	java -ea -Xcheck:jni -Djava.library.path=target -cp "$(MAIN_CLASSES):$(TEST_CLASSES):$(JAVA_TESTCLASSPATH):target/*" org.rocksdb.test.RocksJunitRunner $(JAVA_TESTS)
 
 db_bench: java
 	mkdir -p $(BENCHMARK_MAIN_CLASSES)

java/src/main/java/org/rocksdb/NativeLibraryLoader.java

@@ -72,7 +72,7 @@ public class NativeLibraryLoader {
    *
    * @throws java.io.IOException if a filesystem operation fails.
    */
-  private void loadLibraryFromJar(final String tmpDir)
+  void loadLibraryFromJar(final String tmpDir)
       throws IOException {
     if (!initialized) {
       final File temp;
@@ -80,6 +80,10 @@ public class NativeLibraryLoader {
         temp = File.createTempFile(tempFilePrefix, tempFileSuffix);
       } else {
         temp = new File(tmpDir, jniLibraryFileName);
+        if (!temp.createNewFile()) {
+          throw new RuntimeException("File: " + temp.getAbsolutePath()
+              + " could not be created.");
+        }
       }
 
       if (!temp.exists()) {

java/src/test/java/org/rocksdb/NativeLibraryLoaderTest.java

@@ -4,35 +4,28 @@
 // of patent rights can be found in the PATENTS file in the same directory.
 package org.rocksdb;
 
-import org.junit.ClassRule;
 import org.junit.Rule;
 import org.junit.Test;
 import org.junit.rules.TemporaryFolder;
 import org.rocksdb.util.Environment;
 
 import java.io.IOException;
-import java.nio.file.Files;
-import java.nio.file.Path;
-import java.nio.file.Paths;
+import java.nio.file.*;
 
 import static org.assertj.core.api.Assertions.assertThat;
 
 public class NativeLibraryLoaderTest {
 
-  @ClassRule
-  public static final RocksMemoryResource rocksMemoryResource =
-      new RocksMemoryResource();
-
   @Rule
   public TemporaryFolder temporaryFolder = new TemporaryFolder();
 
   @Test
   public void tempFolder() throws IOException {
-    NativeLibraryLoader.getInstance().loadLibrary(
+    NativeLibraryLoader.getInstance().loadLibraryFromJar(
         temporaryFolder.getRoot().getAbsolutePath());
     Path path = Paths.get(temporaryFolder.getRoot().getAbsolutePath(),
         Environment.getJniLibraryFileName("rocksdb"));
-    assertThat(Files.exists(path));
-    assertThat(Files.isReadable(path));
+    assertThat(Files.exists(path)).isTrue();
+    assertThat(Files.isReadable(path)).isTrue();
   }
 }